External electrodes of the conventional multi-layer piezoelectric element have been formed from an electrically conductive paste having an electrically conductive material such as silver and glass, as disclosed in Patent Document 1. The external electrodes are formed by applying the electrically conductive paste onto side face of a stacked body and subjecting it to baking process.
There have been demands for a greater amount of displacement achieved under a higher pressure as efforts are made for size reduction of the multi-layer piezoelectric element. As a result, the multi-layer piezoelectric element is required to be operable under harsher conditions, namely continuous operation over a long period of time in the presence of higher electric field.    Patent Document 1: Japanese Patent Publication No. 2005-174974